How to Fix a RAD2 Server That Keeps Crashing
RAD2 packs 250+ mods across a dozen-plus dimensions on Minecraft 1.16.5, and most reported crashes trace back to a handful of specific, identifiable causes.
See the RAD2 pack page for boot-tested RAM data before you chase anything else.
1. Wrong Java version
RAD2 needs Java 8. Running Java 11 or newer is a documented, specific cause of crashes for this pack — if the server won't start cleanly, this is the first thing to check.
2. "Incomplete set of tags" on join
This error means the server and client don't agree on the registry of blocks or items — usually a mod failing to register its tags, or a version mismatch between client and server.
Fix: confirm both sides are running the exact same RAD2 version, not just "close enough."
3. Server refuses to start after adding or removing mods
If you've changed the mod list but want to keep the existing world, the server can prompt for confirmation rather than starting normally — this shows up as the server appearing to hang or refuse to boot.
Fix: type /fml confirm into the server console to force it through. This is a safety prompt, not a crash.
4. Extended ticking causing player kicks
RAD2's dozen-plus dimensions and heavy mod count can produce extended tick times that kick players rather than crashing the server outright.
Fix: set max-tick-time=-1 in server.properties to disable the watchdog that's causing the kicks during legitimately slow (not frozen) ticks.
5. RAM below the 8 GB floor
8 GB is RAD2's own recommended floor. Below it, expect lag during exploration or boss fights that's easy to mistake for a mystery bug rather than the simple sizing issue it usually is.
FAQ
What Java version does RAD2 need?+
Java 8 — RAD2 is built on Minecraft 1.16.5, and running Java 11 or newer is a documented cause of server crashes for this pack specifically.
Players get 'incomplete set of tags' when joining — what does that mean?+
The server and client don't agree on the registry of blocks or items, usually because a mod failed to register its tags properly, or client and server pack versions differ. Make sure both sides are on the exact same RAD2 version.
My server is on a wrong-looking RAM count but I didn't change anything — what happened?+
If mods were added or removed and you want to keep the existing world, the server can refuse to start normally and need /fml confirm typed into the console to force it through. This isn't a crash so much as a safety prompt.
Host RAD2 on hardware sized for its 250+ mods
CoalHost pins Java 8 and starts RAD2 servers at the pack's measured 8 GB floor by default, with backups in place before anyone pushes into the next dungeon.
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